Re: [PATCH v2] binder: fix memory leaks of spam and pending work

[Alice Ryhl]

On Fri, Sep 22, 2023 at 7:51 PM Carlos Llamas <cmllamas@xxxxxxxxxx> wrote:
>
> A transaction complete work is allocated and queued for each
> transaction. Under certain conditions the work->type might be marked as
> BINDER_WORK_TRANSACTION_ONEWAY_SPAM_SUSPECT to notify userspace about
> potential spamming threads or as BINDER_WORK_TRANSACTION_PENDING when
> the target is currently frozen.
>
> However, these work types are not being handled in binder_release_work()
> so they will leak during a cleanup. This was reported by syzkaller with
> the following kmemleak dump:
>
> BUG: memory leak
> unreferenced object 0xffff88810e2d6de0 (size 32):
>   comm "syz-executor338", pid 5046, jiffies 4294968230 (age 13.590s)
>   hex dump (first 32 bytes):
>     e0 6d 2d 0e 81 88 ff ff e0 6d 2d 0e 81 88 ff ff  .m-......m-.....
>     04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff81573b75>] kmalloc_trace+0x25/0x90 mm/slab_common.c:1114
>     [<ffffffff83d41873>] kmalloc include/linux/slab.h:599 [inline]
>     [<ffffffff83d41873>] kzalloc include/linux/slab.h:720 [inline]
>     [<ffffffff83d41873>] binder_transaction+0x573/0x4050 drivers/android/binder.c:3152
>     [<ffffffff83d45a05>] binder_thread_write+0x6b5/0x1860 drivers/android/binder.c:4010
>     [<ffffffff83d486dc>] binder_ioctl_write_read drivers/android/binder.c:5066 [inline]
>     [<ffffffff83d486dc>] binder_ioctl+0x1b2c/0x3cf0 drivers/android/binder.c:5352
>     [<ffffffff816b25f2>] vfs_ioctl fs/ioctl.c:51 [inline]
>     [<ffffffff816b25f2>] __do_sys_ioctl fs/ioctl.c:871 [inline]
>     [<ffffffff816b25f2>] __se_sys_ioctl fs/ioctl.c:857 [inline]
>     [<ffffffff816b25f2>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:857
>     [<ffffffff84b30008>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     [<ffffffff84b30008>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Fix the leaks by kfreeing these work types in binder_release_work() and
> handle them as a BINDER_WORK_TRANSACTION_COMPLETE cleanup.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 0567461a7a6e ("binder: return pending info for frozen async txns")
> Fixes: a7dc1e6f99df ("binder: tell userspace to dump current backtrace when detected oneway spamming")
> Reported-by: syzbot+7f10c1653e35933c0f1e@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=7f10c1653e35933c0f1e
> Suggested-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>

Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>